Cheotsarangeul Chaegimjiseyo, Nuna

"Jaegun" and "Gaeun" have known each other since childhood and still live next door to one another. Jaegun has harbored a one-sided love for Gaeun for a very long time, but Gaeun merely dismissed it as a young boy's misunderstanding and married someone else.
Years later, now that Jaegun is an adult, Gaeun finds herself trapped in a marriage to a husband who is both unfaithful and physically abusive. Suffocating yet with nowhere left to turn, Gaeun stands in the emergency stairwell, resolving to end her marriage—and her life—when Jaegun approaches her.
"Are you going to get a divorce? Because if you are, I have something to confess."

Original Webtoon:
Ridibooks, Naver Series, Bomtoon, Lezhin